Phenotypic Variability in PRKCD: a Review of the Literature.

PURPOSE: Protein kinase C δ (PKCδ) deficiency is a rare genetic disorder identified as a monogenic cause of systemic lupus erythematosus in 2013. Since the first cases were described, the phenotype has expanded to include children presenting with autoimmune lymphoproliferative syndrome-related syndromes and infection susceptibility similar to chronic granulomatous disease or combined immunodeficiency. We review the current published data regarding the pathophysiology, clinical presentation, investigation and management of PKCδ deficiency. METHODS: Literature review was performed using MEDLINE. RESULTS: Twenty cases have been described in the literature with significant heterogeneity. CONCLUSION: The variation in clinical presentation delineates the broad and critical role of PKCδ in immune tolerance and effector functions against pathogens.

The Multifaceted Syndromic Primary Immunodeficiencies in Children.

BACKGROUND: Disorders of immunity are poorly recognised in some rare multisystem genetic conditions. We aim to describe syndromic features and immunological defects in children with syndromic primary immunodeficiencies (sPIDs). METHODS: This is a retrospective descriptive study of children aged 0-18 years with sPIDs under the care of the paediatric immunology service at the Bristol Royal Hospital for Children, United Kingdom, from January 2006 to September 2021. RESULTS: sPIDs were identified in 36 patients. Genetic diagnoses which are not commonly associated with PIDs and not included in the International Union of Immunological Societies classification were present in 7/36 (19%): Trisomy 22, Arboleda-Tham syndrome, 2p16.3 deletion syndrome, supernumerary ring chromosome 20 syndrome, Myhre syndrome, Noonan syndrome, and trichothiodystrophy/Cockayne syndrome complex. Recurrent and/or severe infections were the most common clinical features (n = 33, 92%). Approximately half had combined immunodeficiency or antibody deficiency. The most common extra-immunological manifestations include dysmorphism (72%), disorders of nervous (78%), musculoskeletal (69%), haematology/lymphatic (58%), and gastrointestinal, hepatic/pancreatic (58%) systems. CONCLUSIONS: Patients with sPIDs often have multiorgan involvement and some are non-immunologically mediated. There should be a low threshold to clinically assess and investigate for disorders of immunity in any patients with syndromic features especially when they present with recurrent/severe/opportunistic infections, features of immune dysregulation, autoinflammation or lymphoproliferation.

Evaluating UK National Guidance for Screening of Children for Tuberculosis. A Prospective Multicenter Study.

RATIONALE: To identify infected contacts of tuberculosis (TB) cases, the UK National Institute for Health and Care Excellence (NICE) recommended the addition of IFN-γ release assays (IGRA) to the tuberculin skin test (TST) in its 2006 TB guidelines. Treatment for TB infection was no longer recommended for children who screened TST-positive but IGRA-negative. OBJECTIVES: We performed a cohort study to evaluate the risk of TB disease in this group. METHODS: Children exposed to an infectious case of TB in their household were recruited from 11 pediatric TB clinics. TST and IGRA were performed at baseline, with IGRA repeated at 8 weeks and TST repeated if initially negative. Children were treated according to 2006 NICE guidelines and followed for 24 months. MEASUREMENTS AND MAIN RESULTS: Of 431 recruited children, 392 completed the study. We diagnosed 48 (12.2%) cases of prevalent TB disease, 105 (26.8%) with TB infection, and 239 (60.9%) without TB infection or disease. Eighteen children aged 2 years and above had a positive TST but persistently negative IGRA. None received TB infection treatment and none developed TB disease. Ninety (26.1%) children qualified for TB infection treatment according to 2006 NICE guidelines. In contrast, 147 (42.7%) children would have qualified under revised NICE guidance, issued in 2016. CONCLUSIONS: In this low-prevalence setting we saw no incident cases of TB disease in children who were TST-positive but IGRA-negative and did not receive treatment for TB infection. Following the latest NICE guidance, significantly more children will require medication.

Thymus transplantation for complete DiGeorge syndrome: European experience.

BACKGROUND: Thymus transplantation is a promising strategy for the treatment of athymic complete DiGeorge syndrome (cDGS). METHODS: Twelve patients with cDGS underwent transplantation with allogeneic cultured thymus. OBJECTIVE: We sought to confirm and extend the results previously obtained in a single center. RESULTS: Two patients died of pre-existing viral infections without having thymopoiesis, and 1 late death occurred from autoimmune thrombocytopenia. One infant had septic shock shortly after transplantation, resulting in graft loss and the need for a second transplant. Evidence of thymopoiesis developed from 5 to 6 months after transplantation in 10 patients. Median circulating naive CD4 counts were 44 × 106/L (range, 11-440 × 106/L) and 200 × 106/L (range, 5-310 × 106/L) at 12 and 24 months after transplantation and T-cell receptor excision circles were 2,238/106 T cells (range, 320-8,807/106 T cells) and 4,184/106 T cells (range, 1,582-24,596/106 T cells). Counts did not usually reach normal levels for age, but patients were able to clear pre-existing infections and those acquired later. At a median of 49 months (range, 22-80 months), 8 have ceased prophylactic antimicrobials, and 5 have ceased immunoglobulin replacement. Histologic confirmation of thymopoiesis was seen in 7 of 11 patients undergoing biopsy of transplanted tissue, including 5 showing full maturation through to the terminal stage of Hassall body formation. Autoimmune regulator expression was also demonstrated. Autoimmune complications were seen in 7 of 12 patients. In 2 patients early transient autoimmune hemolysis settled after treatment and did not recur. The other 5 experienced ongoing autoimmune problems, including thyroiditis (3), hemolysis (1), thrombocytopenia (4), and neutropenia (1). CONCLUSIONS: This study confirms the previous reports that thymus transplantation can reconstitute T cells in patients with cDGS but with frequent autoimmune complications in survivors.

Clinical spectrum and features of activated phosphoinositide 3-kinase δ syndrome: A large patient cohort study.

BACKGROUND: Activated phosphoinositide 3-kinase δ syndrome (APDS) is a recently described combined immunodeficiency resulting from gain-of-function mutations in PIK3CD, the gene encoding the catalytic subunit of phosphoinositide 3-kinase δ (PI3Kδ). OBJECTIVE: We sought to review the clinical, immunologic, histopathologic, and radiologic features of APDS in a large genetically defined international cohort. METHODS: We applied a clinical questionnaire and performed review of medical notes, radiology, histopathology, and laboratory investigations of 53 patients with APDS. RESULTS: Recurrent sinopulmonary infections (98%) and nonneoplastic lymphoproliferation (75%) were common, often from childhood. Other significant complications included herpesvirus infections (49%), autoinflammatory disease (34%), and lymphoma (13%). Unexpectedly, neurodevelopmental delay occurred in 19% of the cohort, suggesting a role for PI3Kδ in the central nervous system; consistent with this, PI3Kδ is broadly expressed in the developing murine central nervous system. Thoracic imaging revealed high rates of mosaic attenuation (90%) and bronchiectasis (60%). Increased IgM levels (78%), IgG deficiency (43%), and CD4 lymphopenia (84%) were significant immunologic features. No immunologic marker reliably predicted clinical severity, which ranged from asymptomatic to death in early childhood. The majority of patients received immunoglobulin replacement and antibiotic prophylaxis, and 5 patients underwent hematopoietic stem cell transplantation. Five patients died from complications of APDS. CONCLUSION: APDS is a combined immunodeficiency with multiple clinical manifestations, many with incomplete penetrance and others with variable expressivity. The severity of complications in some patients supports consideration of hematopoietic stem cell transplantation for severe childhood disease. Clinical trials of selective PI3Kδ inhibitors offer new prospects for APDS treatment.

The impact of BCG vaccination on tuberculin skin test responses in children is age dependent: evidence to be considered when screening children for tuberculosis infection.

BACKGROUND: Following exposure to TB, contacts are screened to target preventive treatment at those at high risk of developing TB. The UK has recently revised its recommendations for screening and now advises a 5 mm tuberculin skin test (TST) cut-off irrespective of age or BCG status. We sought to evaluate the impact of BCG on TST responses in UK children exposed to TB and the performance of different TST cut-offs to predict interferon γ release assay (IGRA) positivity. METHODS: Children <15 years old were recruited from 11 sites in the UK between January 2011 and December 2014 if exposed in their home to a source case with sputum smear or culture positive TB. Demographic details were collected and TST and IGRA undertaken. The impact of BCG vaccination on TST positivity was evaluated in IGRA-negative children, as was the performance of different TST cut-offs to predict IGRA positivity. RESULTS: Of 422 children recruited (median age 69 months; IQR: 32-113 months), 300 (71%) had been vaccinated with BCG. BCG vaccination affected the TST response in IGRA-negative children less than 5 years old but not in older children. A 5 mm TST cut-off demonstrated good sensitivity and specificity in BCG-unvaccinated children, and an excellent negative predictive value but was associated with low specificity (62.7%; 95% CI 56.1% to 69.0%) in BCG-vaccinated children. For BCG-vaccinated children, a 10 mm cut-off provided a high negative predictive value (97.7%; 95% CI 94.2% to 99.4%) with the positive predictive value increasing with increasing age of the child. DISCUSSION: BCG vaccination had little impact on TST size in children over 5 years of age. The revised TST cut-off recommended in the recent revision to the UK TB guidelines demonstrates good sensitivity but is associated with impaired specificity in BCG-vaccinated children.

Low CD4 T cell immunity to pneumolysin is associated with nasopharyngeal carriage of pneumococci in children.

BACKGROUND: Recent studies in mice have suggested that T cell immunity may be protective against pneumococcal infection. METHODS: CD4 T cell proliferative responses to the pneumococcal proteins pneumolysin (Ply), Ply toxoid (F433), and choline-binding protein A were investigated in peripheral blood mononuclear cells (PBMCs) and adenoidal mononuclear cells (MNCs) obtained from children undergoing adenoidectomy. RESULTS: Ply and F433 induce significant proliferation of CD4 T cells in both PBMCs and adenoidal MNCs, and both memory and naive phenotypes of CD4 T cells proliferated after stimulation. In PBMCs, CD4 T cell proliferation induced by Ply and F433, which was associated with increased production of interferon (IFN)- gamma and tumor necrosis factor (TNF)- alpha , was significantly lower in children who were culture positive for pneumococcus than in those who were culture negative for pneumococcus (P<.05). Between groups, no such difference was observed in adenoidal MNC CD4 T cell proliferation, which was associated with production of IFN- gamma and interleukin (IL)-10. The CD4 T cell proliferation induced by Ply and F433 was inhibited by antibodies to Toll-like receptor 4. CONCLUSION: These data suggest that Ply induces CD4 T cell proliferative responses with production of IFN- gamma and TNF- alpha in PBMCs or of IFN- gamma and IL-10 in adenoidal MNCs, which may be important in modulating pneumococcal carriage in children.

Regulation of production of mucosal antibody to pneumococcal protein antigens by T-cell-derived gamma interferon and interleukin-10 in children.

Nasopharyngeal tonsils (adenoids) are part of human nasopharynx-associated lymphoid tissue, which may play an important role in local defense against pneumococci. Recent studies with animals have suggested that several pneumococcal proteins, including CbpA and pneumolysin (Ply), may be vaccine candidates. Our recent data obtained with children suggest that antibodies to these proteins may protect against carriage. This study was performed to investigate the regulation of the T-cell-dependent antibody responses to CbpA and pneumolysin by cytokines in adenoidal immune cells from children. Adenoidal mononuclear cells (MNC) were cultured with pneumococcal concentrated culture supernatants (CCS) or recombinant proteins. Cytokine expression profiles in adenoidal MNC after antigen stimulation were analyzed by reverse transcription-PCR, protein array analysis, and an immunoassay, along with an antibody production analysis. The roles, interactions, and cellular sources of the main cytokines identified were evaluated further. Pneumococcal CCS induced production of CbpA- and Ply-specific antibodies in association with several chemokines and cytokines, including gamma interferon (IFN-gamma) and interleukin-10 (IL-10) in MNC. The antibody production correlated well with the concentrations of these two cytokines. Addition of recombinant IFN-gamma or IL-10 enhanced antibody production, and monoclonal antibodies to these two cytokines and T-cell depletion significantly reduced antibody production. Intracellular cytokine staining showed that T cells are a major source of IFN-gamma and IL-10. Recombinant Ply and, to a lesser extent, recombinant CbpA induced significant production of IFN-gamma and IL-10 in MNC. T-cell-derived IFN-gamma and IL-10 may be key regulators of production of mucosal antibody to pneumococcal protein antigens in the nasopharynx and may play an important role in local protection against pneumococcal infection in children.

Serum and mucosal antibody responses to pneumococcal protein antigens in children: relationships with carriage status.

Streptococcus pneumoniae causes significant morbidity and mortality especially in children. Some pneumococcal protein antigens can protect mice against infection. Little information is available concerning the nature of naturally acquired protective immunity to pneumococci in humans induced by these antigens. This study investigates the relationships between systemic and local antibody production and carriage in children. Children undergoing adenoidectomy (n=112, ages 2-12 years) were studied. Nasopharyngeal swabs were collected for pneumococcal culture. Serum and saliva were assayed for antibodies to several pneumococcal proteins: choline binding protein A (CbpA), pneumolysin (Ply), pneumococcal surface adhesin A (PsaA) and pneumococcal surface protein A (PspA). Adenoidal mononuclear cells (MNC) were cultured with pneumococcal culture supernatants or recombinant proteins. Cell culture supernatants were analyzed for antigen-specific antibodies. Carriage rates fell with age and serum levels of anti-CbpA, Ply and PspA rose. Anti-CbpA and -Ply serum and salivary IgG antibody levels were higher in children who were culture negative than those who were colonized. Antigen stimulation increased respective antigen-specific IgG production by adenoidal MNC and these responses were greater in those who were colonized than in culture-negative children. Antibodies to CbpA and Ply may protect children aged 2 years and older against pneumococcal colonization. Adenoids may be important local induction and effector sites for both mucosal and systemic antibody production to pneumococcal proteins in children.